Mounting 618 and 670 to KF-IV

[rdooley79]

I cruise at 6000, redline is set at 6350. Cruise at 6000 is about 83mph indicated but that's at 7500msl so at sea level you'll get better performance.
You could get more power out of this engine but it's tuned for reliability and longevity.
Spinning the engine faster means the prop spins faster so that introduces gearing considerations. The RPM that the 670 likes to run is right at 5900-6000.
It just humms right along at that power setting. Fuel burn is averaging right around 4.5-5gph. That's about the same as a 582.

I didn't do any port timing changes but it did come freshly built with an hour on Rotax Rick's test stand, ready to go. The exhaust timing is done with the exhaust which is critical for these engines to make power with a nice flat power curve, consistent power throughout the rpm band. The exhaust Rick has available is the "breakthrough" for the 670 to be used on aircraft. Dual Ducati electronic ignition is a must to be even considered as a serious aircraft engine to me.

Mounting the exhaust is the trick with the 670. It's a larger exhaust and takes up more space.

The prop pitch tends to work best if you pitch it a little course. I'm running a 3 blade Warp Drive, 72" 3:1 gearbox. The 670 has more torque and can swing a loaded prop better than a 582 and provides good thrust as well.

Jetting needs to be watched, especially at a mile high field elevation. Rick likes to run these engines rich, 40:1 and big main jets. I've had to go down in jet sizes because of my altitude. I'm running 162's with both needles dropped to the top notch. This makes the plugs look nice rich brown without being too rich. Rick sets them up at sea level with 180's, needles set to the middle notch. This made my engine cough and stutter but once I jetted it like a rich 582, it ran GREAT! I might go down to 160's but I'm watching the plugs as the true indicator, NOT egt's. They're showing 900 at WOT, 1150 at 5700. It's weird but talking with Rick about it he says that's about right and is typical. Also he confirmed the prop pitch being a bit on the course side working better also. I can say that it's running great now.

Swapping out the 582 for the 670 is a fantastic upgrade. Made my plane fly so much better. If only I could fly as well as the plane! Working on that.